class_docstr: Callable object storing the details of one alias.
  
  Instances are registered as magic functions to allow use of aliases.
code: def __init__(self, shell, name, cmd):
      self.shell = shell
      self.name = name
      self.cmd = cmd
      self.__doc__ = "Alias for `!{}`".format(cmd)
      self.nargs = self.validate()
  
imports: import os
  import re
  import sys
  from traitlets.config.configurable import Configurable
  from .error import UsageError
  from traitlets import List, Instance
  from logging import error
label_desc: Use image node_id 1 to create a new Alias object from inherited base classes: object with example: obj = Alias(shell, name, cmd)